If you take isolated examples from anyone's life, without considering the whole of their life, you can make them look like whatever you want them to look like.
This is not a "isolated" example and their whole lives where about having sexual relations and they even wrote it into there made up doctrines along with any other nonsense they could think of to gain power and money. We would throw these men into prison today as child molesters and perverts, not to mention con-artist.
It is quite obvious how you feel about the founders of the Church of Jesus Christ of Latter-day Saints. Now show the fruits you said must accompany this sort of foundation. Show how the fruits that grow from the lives of the majority of the followers of these corrupt men confirm your conclusions.